1. Field of the Invention
The present invention relates to a solenoid-operated valve, which is drivable by applying a first voltage to a solenoid coil, and which is maintained in a driven state by applying a second voltage, and to a solenoid-operated valve-driving circuit, which applies the first voltage or the second voltage to the solenoid coil.
2. Description of the Related Art
A technical concept is known, in which a solenoid-operated valve is arranged at an intermediate position of a flow passage, and wherein when a voltage is applied to a solenoid coil of the solenoid-operated valve from a solenoid-operated valve-driving circuit, the solenoid-operated valve is energized for opening and closing the flow passage (see Japanese Laid-Open Patent Publication Nos. 7-331718 and 2000-257744).
The present applicant has confirmed the use of a solenoid-operated valve 206, based on the use of a solenoid-operated valve-driving circuit 200, 220, as shown in FIGS. 17 and 18.
In the case of the solenoid-operated valve-driving circuit 200 shown in FIG. 17, when a switch 202 is closed, a power source voltage V0 from a DC power source 204 is applied to a solenoid coil 208 of the solenoid-operated valve 206, and the solenoid-operated valve 206 is placed in a driven state, which is brought about by the electromagnetic force resulting from the current that flows through the solenoid coil 208.
In the solenoid-operated valve-driving circuit 200, a resistor 210 and an LED 212, and a diode 214 are electrically connected in parallel respectively to the solenoid coil 208. Therefore, when the LED 212 emits light, the fact that the solenoid-operated valve 206 is in a driven state can be visually recognized. A counter-electromotive force, which is generated in the solenoid coil 208 when application of the power source voltage V0 to the solenoid coil 208 is stopped, is attenuated in a short period of time by the diode 214.
In the case of the solenoid-operated valve-driving circuit 220 shown in FIG. 18, when the switch 202 is closed, a transistor 222 is changed from an OFF state to an ON state, and a power source voltage V0, as a first voltage, is applied to the solenoid coil 208. When a predetermined period of time elapses from closing of the switch 202, and charging of a capacitor 226 is completed by means of a resistor 224, then the transistor 222 is changed from an ON state to an OFF state as a result of the charging voltage of the capacitor 226. Accordingly, the power source voltage V0 is subjected to voltage division by a resistor 228. A second voltage, generated as a result of such a voltage division, is applied to the solenoid coil 208. Thus, the solenoid-operated valve 206 can be maintained in a driven state.
In relation to the solenoid-operated valve-driving circuit 200 shown in FIG. 17, the same power source voltage V0 is applied to the solenoid coil 208 during driving of the solenoid-operated valve 206, as well as during the time region in which the driven state is maintained. Therefore, excessive electric energy is supplied to the solenoid coil 208 during the time region in which the driven state is maintained. As a result, electric power is wastefully consumed.
On the other hand, in relation to the solenoid-operated valve-driving circuit 220 shown in FIG. 18, a power source voltage V0 (first voltage) is applied to the solenoid coil 208 during driving of the solenoid-operated valve 206, whereas a second voltage, which is lower than the power source voltage V0, is applied during the time region in which the solenoid-operated valve 206 is maintained in a driven state. Therefore, it is possible to reduce electric power consumption by the solenoid coil 208, during the time region in which the solenoid-operated valve 206 is maintained in a driven state, as compared with the solenoid-operated valve-driving circuit 200.
However, in the case of the solenoid-operated valve-driving circuit 220, the power source voltage V0 is subjected to voltage division by means of the resistor 228, in order to generate the second voltage, which is then applied to the solenoid coil 208. Therefore, electric power is wastefully consumed in the resistor 228.
Further, in the case of the solenoid-operated valve-driving circuit 220, ON and OFF states of the transistor 222 are switched, on the basis of the charging/discharging time of the capacitor 226 through the resistor 224. Therefore, when the solenoid-operated valve-driving circuit 220 is stopped, for example due to a power failure, then the solenoid-operated valve-driving circuit 220 cannot be restarted in a short period of time, and/or the solenoid-operated valve 206 cannot be changed over quickly into the time region during which the driven state is maintained.